Substitution reactions in aqueous solution

The substitution reaction in aqueous solution is the most common method used for the synthesis of metal complexes. The method involves a reaction between a metal salt in water solution and a coordinating agent. For example, the complex [Cu(NH3)4]S04 is readily prepared by the reaction (1) between 

Substitution reactions of metal complexes can also be fairly slow and, for such systems, more drastic experimental conditions are required. To prepare K3[Rh(C204)3], one must boil a concentrated aqueous solution of K3[RhCl6] and K2C2O4 for 2 hours and then evaporate it until the product crystallizes from the solution, reaction (2). 

It is also possible that more than one type of ligand will be replaced during a reaction. Thus [Co(en)3]Cl3 may be prepared by reaction (3). Because this reaction is rather slow at room temperature, it is carried out on a steam bath. 

Since the nitrogen molecule is isoelectronic with CO, CN, and NO, all of which form a variety of stable molecules, then N2 should also have some tendency to coordinate with metals. Although coordination chemists had long tried to make N2 complexes, the first successful synthesis (of [Ru(NH3)5(N2)]Br2) was not achieved until 1965. This important discovery was immediately followed by intensive research, and many different dinitrogen-metal (N2-M) complexes were prepared. In several cases, it was found that simple ligand substitution (6) can generate the desired product. 

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Nucleophili substitution, in phosphate esters, mechanism and catalysis of, 25, 99 Nucleophilic substitution, single electron transfer and, 26, 1 Nucleophilic substitution reactions in aqueous solution, 38, 161 Nuckophilic vinylic substitution, 7, 1... 

Solvent effects, reaction coordinates, and reorganization energies on nucleophilic substitution reactions in aqueous solution, 38, 161... 

Short-lived organic radicals, electron spin resonance studies of, 5, 53 Small-ring hydrocarbons, gas-phase pyrolysis of, 4, 147 Solid state, tautomerism in the, 32, 129 Solid-state chemistry, topochemical phenomena in, 15, 63 Solids, organic, electrical conduction in, 16, 159 Solutions, reactions in, entropies of activation and mechanisms, 1, 1 Solvation and protonation in strong aqueous acids, 13, 83 Solvent effects, reaction coordinates, and reorganization energies on nucleophilic substitution reactions in aqueous solution, 38, 161 Solvent, protic and dipolar aprotic, rates of bimolecular substitution-reactions in,... 

Solvent effects, reaction coordinates, and reorganization energies on nucleophilic substitution reactions in aqueous solution, 38, 161 Solvent, protic and dipolar aprotic, rates of bimolecular substitution-reactions in, 5,173 Solvent-induced changes in the selectivity of solvolyses in aqueous alcohols and related mixtures, 27, 239... 

This helped to derive the Hughes-Ingold rules for predicting the effect of solvent polarity on the reaction rate.1 We have used the combined QM-MOVB/MM method to study three nucleophilic substitution reactions in aqueous solution, which are summarized below. 

The iridium(III) pentaamine complexes Pr(X)(NH3)5]2+ undergo octahedral substitution reactions in aqueous solution, similar to Co111 and Rh111 analogues.221 [Ir(X)(NH3)5]2+ (X = N03, Cl, Br, I) undergoes aquation (reaction 63) with the reactivity increasing in the order... 

Ligand-substitution reactions in aqueous solutions rarely proceed directly. Instead, the leaving ligand is first replaced by H2O, which is present in aqueous solution at a concentration of 55 M, the entering ligand then substitutes the metal-bound H2O (M-OH2) inthe so-called anationreaction. Therefore, the rate constant of forward reactions, which could be considered as the reactivity of aquo-metal species, will parallel the order of water substitution in the inner coordination sphere of the corresponding metal ions Cs > Ba > Hg2+ > K+ > Cr2+ Cu + > Na+ > Sr + Li+ > Ca + > Cd + > Mn2+ Zn + > Fe + > Co + > Mg + > nP+ > Pd + > Pt + > cases, the interactions between... 

Rate and Equiubriijm Constant Data for Axial Ligand Substitution Reactions in Aqueous Solutions... 

Although it is convincing that metaphosphate ion is not a free intermediate in substitution reactions in aqueous solution, this does not exclude the possibility of reactions of related species proceeding via analogous intermediates. Reactions of thiophosphate monoesters are more rapid than those of phosphate monoesters. If three sulphur atoms replace three of the oxygens of metaphosphate, a stable salt can be isolated (Roesky et al, 1986). Harnett and Lowe (1988) examined the stereochemical course of the non-enzymic hydrolysis of adenosine (P- O, thio) diphosphate in In... 

The most fundamental substitution reaction in aqueous solution, water exchange, reaction (22), has been studied for a variety of metal ions (Figure 6.3). Exchange of water in the coordination sphere of a metal with bulk solvent water occurs very rapidly for most metal ions, and therefore the rates of these reactions were studied primarily by relaxation techniques. In these methods, a system at equilibrium is disturbed, for example, by a very sudden increase in temperature. Under the new condition— higher temperature—the system will no longer be at equilibrium. The rate of equilibration can then be measured. If one can change the temperature of a solution in 10 s, then one can measure the rates of reactions that take longer than 10 s. 

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